It is unfair for anyone to rub the ball on the ground for any reason, interfere with any of the seams or the surface of the ball, use any implement, or take any other action whatsoever which is likely to alter the condition of the ball

Shoaib Akhtar has become only the second player in the history of international cricket to receive a ban for ball-tampering.

The Pakistani paceman, no stranger to controversy, was first found guilty of cheating in this manner in a Test against Zimbabwe in Harare in November 2002.

And now he must serve a two-match ban after repeating the illegal practice on Tuesday in a one-day match in Sri Lanka against New Zealand.

For the record, Pakistan won both games. Shoaib took 3-36 in the one-dayer and 7-118 in the Test match.

The principle is simple, yet completely against the spirit of the game. But why do bowlers do it and how exactly do they achieve it?

As a ball loses its early shine, it begins to swing less, and it is not until it gets old and rough that it begins to deviate again, a process known as reverse swing.

But bowlers occasionally feel the need to encourage reverse swing early in order to take their wickets.

As the leather on a ball begins to crack after hitting the boundary boards a number of times, fingernails can be used to rough up one side.

The laws of the game allow fielders to polish, clean or dry the ball, but that is as far as they can go.

It is not pointing the finger to say it is a practice most commonly associated with Pakistanis.

Former Pakistan captain Imran Khan admitted in 1994 that he had "occasionally scratched the side of the ball and lifted the seam".

He added: "Only once did I use an object. When Sussex were playing Hampshire in 1981 the ball was not deviating at all.

"I got the 12th man to bring out a bottle top and it started to move around a lot."

Waqar and Shoaib: The only players to be banned for ball-tampering

Waqar Younis was given a one-match suspension two years ago after he was seen on television lifting the seam during a one-day international against South Africa.

For many it brought back memories of the summer of 1992 when the heated Test series between England and Pakistan was followed by an even more acrimonious one-day series.

Umpires Ken Palmer and John Hampshire ordered for the ball to be changed during the interval of the Lord's one-day international.

But the ICC later refused to release either the ball or the umpires' report to the media.

Allegations flew between players, with Imran taking on Ian Botham and Allan Lamb in a libel suit, and emerging with a £400,000 award.

The strength of feeling generated by the claims, along with allegations of racism, reared up again in November 2001, when Sachin Tendulkar was implicated in the practice.

After a fine was handed out to the Indian legend, match referee Mike Denness saw his effigy burned in the streets of Delhi.